Crossed field ignition plug system



Nov. 23, 1965 E. H. DINGMAN CROSSED FIELD IGNITION PLUG SYSTEM Filed Feb. 23, 1962 INVENTOR.

United States Patent 3,219,866 CROSSED FIELD IGNITION PLUG SYSTEM Edward H. Dingman, Littleton, Colo., assignor to The Martin-Marietta Corporation, Baltimore, Md., :1 corporation of Maryland Filed Feb. 23, 1962, Ser. No. 175,203 Claims. (Cl. 313-118) This invention relates to a novel and improved ignition device; and more particularly relates to an ignition plug system having crossed electrical and magnetic fields and which is characterized by high energy, controlled ignition with low voltage requirements.

Conventional spark plugs and similar ignition devices tend to burn at the points as the arc is localized. Also, the gap required dictates that high voltages be used, accompanied by relatively low currents and temperatures at the arc. t is therefore a principal object of this invention to provide for a new and improved ignition device which overcomes the above and a number of other disadvantages in the prior art by enabling use of a low voltage, low impedance ignition coil to attain greatly increased energy efiiciency levels in the are produced.

It is another object of the present invention to make provision for an ignition plug having increased life, im-

proved impedance matching between the ignition coil and the load represented by the spark arc, and affording a self-cleaning action on the electrodes due to the very high velocity developed in the ionized gas of the spark; moreover, where the plug is constructed and arranged to produce a low tension, high energy are at a high temperature with minimum burning and depositing at the electrodes.

It is a further object to provide for an ignition plug which is simplified in design and construction with high energy, controlled ignition at a low voltage; and more specifically attains a low voltage gap breakdown coupled with a long gap working discharge whereby to produce improved spark gap-to-coil impedance matching and nonpoint dwelling of the spark to reduce spark erosion and scouring.

The device of the present invention is based on a unique application of the rail gun principle to ignition systems whereby an external magnetic field is so disposed in relation to divergent electrodes as to produce controlled directional advance of an arc across the electrodes for high current, low voltage ignition with highly efficient impedance matching. The electrical field developed at the electrodes is crossed to the magnetic field and in such a way that the lines of magnetic flux will not only-spread but physically displace the are combined with an actual change in gap length across the electrodes. A number of benefits and advantages are derived from this as will become more readily apparent from the following detailed description of preferred and alternate forms of the present invention, taken together with the accompanying drawings, in which:

FIGURE 1 is a longitudinal section view of a preferred form of the present invention together with an ignition circuit for energization thereof;

FIGURE 2 is an end view of the preferred form shown in FIGURE 1;

FIGURE 3 is a schematic view illustrtaing the interaction between the magnetic and electric fields in displaciing the arc along the electrodes;

FIGURE 4 is a longitudinal section view of an alternate form of the present invention; and

FIGURE 5 is an end view of the alternate form shown in FIGURE 4.

Referring in detail to the drawings, the ignition plug of FIGURES 1 and 2 is broadly comprised of a body 12 being generally tubular in cross section and having a threaded sleeve 14, a tool or wrench-receiving portion 15 and an upper extremity 16 including an inturned flange or rim 17. Insulation 20 is inserted within the body having a stepped portion 21 abutting the flange 17 to retain the insulation 20 within the body and an up wardly tapering portion 22. A central passage 23 extends the substantial length of the insulation into communication with an outwardly divergent cavity area 24 formed at the lower end of the insulative portion 20.

A high voltage conductor wire 26 extends through the passage 23 having an upward projection 27 for connection into ignition circuit 28. The latter is of conventional design and for example may include a D.-C. source 29 and high voltage coil 30. In the cavity 24, a pair of divergent, diametrically opposed electrode rods 31 and 32 are stationed therein and following the outwardly divergent contour of the cavity walls. Each electrode rod is elongated and of generally cylindrical configuration with upper relatively near ends 33 and 34 terminating in break points 35; lower, divergent ends 36 and 37, respectively, terminate flush with the lower extremity of the plug. End portion 36 of electrode 31 is connected to an inwardly projecting portion 38 of the sleeve 14; whereas, the end 37 for electrode 32 is insulated from ground, its upper end 34 being connected into the conductor rod 26.

As best seen from a consideration of FIGURES l and 2, a pair of magnetic pole pieces 39 and 40 project inwardly from the sleeve 14 through the insulation in diametrically opposed relation to one another and in normal, coextensive relation to the electrodes 31 and 32. In the particular relationship shown, the electrode 32 is con nected to the positive side of the coil 30 and the electrode 31 is connected to the negative side. The magnetic pole pieces are given a definite polarity in relation to the electrode polarity so that according to the direction of current flow through the electrodes the lines of flux between the magnetic pole pieces together with those self-induced in the electrical field will have a resultant force causing the arc developed between the electrodes to move downwardly from relatively near ends 33 and 34 to divergent ends 36 and 37; or in other words, the resultant force will cause the arc to move in the direction of divergence of the electrodes away from the break points 35. Basically, therefore, where the magnetic field is positioned in crossed or normal relation to the electrical field, the direction of current flow from the ignition circuit through the electrodes should be established sothat the polarities of the electrodes and the magnetic field will agree, thus causing the arc to move outwardly in the direction of divergence.

The above relation is schematically shown in FIGURE 3 where the pole pieces are shown having magnetic lines of flux M and the arc, designated at A, passes in a direction between the electrodes from positive to negative. The self-induced field of the arc will have lines of flux E traveling in a clockwise direction so that the lines of flux M will tend to agree in direction with the flux lines E and will therefore pass over the arc to force the arc downward along the electrodes. From this it will be seen that by combining a narrow break-down gap at the break points 35 with a wide operating gap along the length of the electrodes and using a magnetic field to drive the are from the narrow to the wide gap, a greatly improved impedance match can be obtained between the plug and ignition coil. As a result, the plug may be termed an automatic impedance matcher requiring lower impedance and voltage but with relatively high current and temperature characteristics. Thus, for a given voltage the energy developed across the arc is 35 times that delivered in conventional plug systems and makes it highly valuable for higher speed engines and in starting cold internal combustion engines of all types. Furthermore, the plug is selfcleaning since the magnetic field drives the arc at a sufficient velocity to dislodge any carbon which might otherwise collect in the ignition chamber around the electrodes. As an example, for an electrode pair diverging from 0.0625 -to 0.25 inch, and given a voltage level on the order of 2,000-4,000 volts, the current flow would be on the order of 5 to amperes.

In the alternate form shown in FIGURES 4 and 5, the ignition device 40 is again comprised of a body shell 12 having an inner insulative portion 20. The shell 12 and insulative portion 20 are constructed similarly to those shown in the preferred form and accordingly, corresponding parts are similarly identified. A conductor 26' extends through central passage 23 in the insulative portion 20 and along the longitudinal axis of the plug into communication with a cylindrical cavity area 44 at the lower end of the insulative portion. In this form, however, a concentric ring electrode plug is formed whereby the spark will move angularly rather than linearly between the electrodes. To this end, a magnetic core 46 is positioned in inner spaced coaxial relation within the cavity 44 being electrically connected at one end to the conductor 26 and projecting outwardly beyond the end of the plug. The magnet has north and south poles as indicated, and mounted concentrically on the body of the magnet 46 adjacent to the lower extremity of the plug is an inner ring electrode 48, generally semi-cylindrical in configuration, and projecting across the space formed between the magnet and the cavity. An outer spaced concentric ring electrode 50 forms an inward extension at the lower end of the plug device having an inwardly projecting break point 51, opposite break point 49 of the inner ring electrode 48, in order to form a narrow breakdown gap therebetween. The ignition circuit, not shown, is connected across the electrodes with the polarity indicated, and for current flow and magnetic polarity as shown, the arc will move counterclockwise from the point of breakdown. Of course, should the polarity of voltage or field be reversed the arc would move in the opposite direction. Again, the result is the same as in the preferred form; that is, the magnetic field established in crossed relation to the electrical field will exert a force on the are causing it to advance from the narrow breakdown gap through a relatively wide operating gap formed in the annular space between the inner and outer concentric electrodes.

In both forms, the insulative portion is preferably composed of a ceramic material and the magnetic members are composed of a high temperature magnetic material. The electrodes may be of any desired cross-sectional configuration and length and the angle of divergence and spacing between electrodes will of course be controlled in accordance with the voltage level developed in the ignition coil. Moreover, in both forms the particular design and construction of the plugs results in greatly improved plug life, better impedance matching between the ignition coil and load represented by the arc, and self-cleaning action of the electrodes due to the very high velocity of the ionized gas of the spark. As the breakdown point separation is quite small a lower voltage can be used which in turn permits the use of higher current so that it is possible to operate with a much hotter spark. As the spark can be driven faster than the flame propagation, a larger volume of fuel mixture can be contacted thus improving ignition in the automotive type engine.

It is to be understood from the foregoing that various changes and modifications may be made in the particular construction and arrangement of parts in the preferred and alternate forms of invention without departing from the scope thereof as defined by the appended claims.

What is claimed is:

1. In an ignition system, an ignition plug comprising at least one pair of electrodes having a relatively narrow breakdown gap and diverging outwardly away from said breakdown gap to form a relatively wide operating gap therebetween, a magnetic field member coextensive with and normal to the electrical field of said electrodes having a polarity in relation to the current flow of an are discharged across said electrodes to force the arc in the direction of divergence of said electrodes and away from the breakdown points.

2. In an ignition system, a spark plug comprising a pair of electrodes having breakdown points disposed relatively close to each other and an operating gap therebetween, the distance separating said electrodes at said operating gap being greater than the distance separating said breakdown points, a magnet having a magnetic field extending normal to the self-induced electric field of said electrodes, and said magnet having a polarity in relation to the direction of current flow across said electrodes to force the arc in a direction away from the breakdown points and along the operating gap between said electrodes.

3. In an ignition system according to claim 2, said electrodes being disposed in inner and outer spaced concentric relation to one another.

4. In an ignition system including an ignition circuit, a spark plug comprising an insulator including an outwardly divergent cavity at one end, a pair of electrodes disposed within said cavity and being connected to said ignition circuit to produce an arc discharge across said electrodes, breakdown points between said electrodes disposed relatively close to each other and said electrodes diverging outwardly through said cavity away from said breakdown points to form a relatively wide operating gap therebetween, the distance separating said electrodes at said operating gap being greater than the distance separating said breakdown points, magnetic members coextensive with said electrodes and positioned in surrounding relation to said cavity having poles diametrically opposite to one another and producing a field normal to the field of said electrodes, said magnet having a polarity in relation to the direction of current How of the arc across said electrodes to force the arc in the direction away from the breakdown points and along the operating gap between said electrodes.

5. In an ignition system having a voltage source and an ignition coil, the combination of a spark plug comprising an insulator including a generally cylindrical cavity at one end thereof, a pair of inner and outer spaced concentric electrodes positioned at the outer end of the cavity, breakdown points between said electrodes, and a magnet extending through said cavity and projecting outwardly beyond the end of said cavity in inner concentric relation to said electrodes, said magnet having a polarity in relation to current flow through said electrodes to force the arc to travel away from the breakdown points and along a gap formed between said electrodes.

References Cited by the Examiner UNITED STATES PATENTS 1,244,844 10/1917 Dodds 313157 X 2,008,617 7/1935 Lampitt fl 313157 X GEORGE N, WESTBY, Primary Examiner, 

1. IN AN IGNITION SYSTEM, AN IGNITION PLUG COMPRISING AT LEAST ONE PAIR OF ELECTRODES HAVING A RELATIVELY NARROW BREAKDOWN GAP AND DIVERGING OUTWARDLY AWAY FROM SAID BREAKDOWN GAP TO FORM A RELATIVELY WIDE OPERATING GAP THEREBETWEEN, A MAGNETIC FIELD MEMBER COEXTENSIVE WITH AND NORMAL TO THE ELECTRICAL FIELD OF SAID ELECTRODES HAVING A POLARITY IN RELATION TO THE CURRENT FLOW OF AN ARC DISCHARGED ACROSS SAID ELECTRODES TO FORCE THE ARC IN THE DIRECTION OF DIVERGENCE OF SAID ELECTRODES AND AWAY FROM THE BREAKDOWN POINTS. 